Bioturbation is the process by which the original layering of sediments is displaced by burrowing organisms. All types of worms, crabs or burrowing sea urchins can seriously rearrange a sediment. The original layering, the sorting of sediment grains or such sedimentary structures as graded bedding can be disrupted in the process. Bioturbation in a sediment is also an indication that anoxic (oxygen-free) circumstances have not prevailed.

In layers of sedimentary rock there is relatively often evidence of bioturbation, such as passageways created by various organisms. In many cases it is unknown which organisms have caused the bioturbation because their fossils are not preserved. When a lot of bioturbation has taken place in sedimentary soil, a homogeneous texture develops in which the individual burrowing traces are no longer recognizable. In lithified sedimentary rock, sometimes the bioturbation is so pervasive that it completely obliterates the sedimentary structures or fine layering.

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